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AWS Auth

AWSOfficialPublished by AWS

  • Skill
  • Tool integration
  • Cloud and DevOps
  • Apache-2.0
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From the author

Adds user authentication to web and mobile apps with Amazon Cognito (user pools and identity pools) and the AWS Amplify client auth libraries. Covers sign-up/sign-in flows and the login page (Cognito-hosted UI / managed login), MFA, password policies, OAuth 2.0 / OIDC flows (auth-code + PKCE, client credentials), social/SAML federation, tokens (ID/access/refresh, rotation, revocation, storage), Cognito Lambda triggers, identity pools (temp AWS creds), and gating API Gateway (or ALB) routes to signed-in users via Cognito/JWT authorizers. Applies when adding a login or sign-up page, configuring a user pool or app client, choosing user pool vs identity pool, wiring social/SAML, refreshing tokens, requiring sign-in on an API Gateway or ALB, or debugging redirect_uri/token/MFA/CORS/federation errors. Does NOT cover Amplify Gen2 backend definitions (defineAuth, npx ampx → aws-amplify), IAM/STS/Identity Center (→ aws-iam), or API Gateway/Lambda resource config beyond the authorizer (→ aws-serverless).
— the description by AWS

AutoGineer summary

Written by AutoGineer from the skill’s own files, not by the author

This skill provides guidance on integrating Amazon Cognito user pools and identity pools into web and mobile applications. It covers the full lifecycle of authentication, including sign-up/sign-in flows, managed login, MFA, OAuth 2.0/OIDC standards, and token management. It also details how to secure API Gateway or ALB routes using Cognito authorizers and how to vend temporary AWS credentials to clients via identity pools. The skill emphasizes secure practices, such as using PKCE for public clients and avoiding common pitfalls like client secret exposure or improper identity pool role configuration.

What it does

  • Configures Amazon Cognito user pools for user directory and authentication management.
  • Implements OAuth 2.0 and OIDC flows, including authorization code grant with PKCE.
  • Secures API Gateway and ALB routes using Cognito/JWT authorizers.
  • Manages identity pools to provide temporary AWS credentials to authenticated clients.
  • Handles token lifecycle, including rotation, revocation, and secure storage.
  • Integrates social and SAML federation for external identity providers.

When to use it

  • When adding sign-up or login functionality to a web or mobile application.
  • When you need to gate API endpoints to ensure only authenticated users can access them.
  • When your client application requires direct access to AWS services like S3 or DynamoDB.
  • When configuring MFA, password policies, or custom authentication challenges.
  • When troubleshooting authentication errors like redirect mismatches, CORS issues, or token validation failures.

Advantages

  • Provides clear distinctions between user pools and identity pools to prevent common architectural errors.
  • Highlights critical security practices like avoiding client secrets in public clients.
  • Includes specific guidance on avoiding destructive 'full replace' API calls.
  • Offers a structured approach to troubleshooting common authentication and federation issues.
  • Aligns with industry-standard security patterns for token handling and API protection.

Usage examples

“How do I set up a user pool for a React app with hosted UI?”
The agent provides steps to create a user pool, configure a public app client, enable the hosted UI with authorization code grant and PKCE, and wire the Amplify client library.
“My API Gateway is returning 401 errors for valid tokens, what should I check?”
The agent guides you to verify the token type, check the issuer and audience configuration in the JWT authorizer, and ensure the correct token is being sent in the Authorization header.
“How do I allow my mobile app users to upload files directly to S3?”
The agent explains how to set up an identity pool that trusts your user pool, maps authenticated users to an IAM role with S3 permissions, and vends temporary credentials.
“How do I add Google login to my Cognito user pool?”
The agent outlines the process of registering Google as an IdP in the user pool, mapping attributes, and updating the app client to include the provider.

Install

  1. Download the skill as a ZIP:

    https://mp-staging.autogineer.com/agent-skills/aws/aws-auth/download
  2. Unzip it into the cross-client skills folder of your project:

    mkdir -p .agents/skills && unzip aws-auth.zip -d .agents/skills

Documentation by AWS

AWS Auth (Amazon Cognito)

Application-level user authentication and authorization with Amazon Cognito and the Amplify client auth libraries. Verify specific limits, quotas, and exact API shapes against official AWS documentation when precision matters; trust the docs over memory when they conflict.

Recommended: The AWS MCP server provides streamlined access to the AWS APIs used in this skill (Cognito user pool/app client/identity pool setup, API Gateway authorizers). If it is unavailable, the AWS CLI commands shown throughout work directly — the skill has no hard dependency on MCP.

When NOT to use: Amplify Gen2 backend code (defineAuth, amplify/auth.ts, npx ampx); IAM policy/role/trust-policy authoring, STS, or IAM Identity Center console SSO; API Gateway route/integration setup or Lambda function implementation (this skill covers only the Cognito/JWT authorizer configuration and the purpose of Cognito Lambda triggers).

User Pool vs Identity Pool — pick first

These are different services that are frequently confused. Most apps need a user pool; add an identity pool only if the client must call AWS services directly.

You need...UseWhy
Sign-up / sign-in, user directory, issue JWTsUser poolIt authenticates users and is an OIDC IdP
The signed-in client to call S3/DynamoDB/etc. directly with AWS credentialsIdentity poolIt exchanges a token for temporary AWS credentials via STS
Both (sign in, then hit AWS resources from the browser/app)User pool → identity poolIdentity pool trusts the user pool as its IdP

If your app only calls your own backend/API, you do not need an identity pool — send the user pool token to your API. See identity-pools.md.

Critical Warnings

update-user-pool-client and set-identity-pool-roles are FULL REPLACE, not partial updates: Any field you omit is reset to its default — calling update-user-pool-client with only the fields you want to change silently wipes ExplicitAuthFlows, token validity, EnableTokenRevocation, refresh-token rotation, and read/write attributes; set-identity-pool-roles likewise replaces the whole roles + RoleMappings structure. Always read-modify-write: describe-user-pool-client (or get-identity-pool-roles) first, then re-send every existing field plus your change. In an agent context the wipe is invisible — the call succeeds and only breaks later when a user hits the missing flow. See managed-login-oauth.md and identity-pools.md.

Don't use the implicit grant for new apps: The implicit grant (response_type=token) is legacy and returns tokens in the URL fragment. Use the authorization code grant with PKCE (response_type=code + code_challenge) for SPAs and mobile — public clients, no client secret. See managed-login-oauth.md.

Don't store refresh tokens in localStorage for high-value apps: localStorage is readable by any injected script (XSS). The Amplify client library defaults to localStorage; switch to cookieStorage, keep refresh-token lifetime short, and enable refresh token rotation + token revocation on the app client. See tokens-and-sessions.md.

Access-token claim customization needs a paid feature plan: The pre token generation trigger customizes the ID token on the entry-level plan (V1), but customizing the access token (V2/V3) requires a paid feature plan — check the Cognito feature plans documentation for which plan currently includes this, as plan names and inclusions can change. Don't assume access-token claims work on the entry-level plan. See lambda-triggers.md.

App client secret + SPA = broken auth: A public client (browser/mobile) must have no client secret. If a secret is set, token calls fail unless a SECRET_HASH is sent, which a browser cannot protect. Generate a secret only for confidential (server-side) clients.

Don't bulk admin-confirm-sign-up UNCONFIRMED users: When users are stuck UNCONFIRMED, prefer resend-confirmation-code so each user re-verifies via confirm-sign-up and proves email ownership (the code likely expired or went to spam). admin-confirm-sign-up flips the status instantly but confirms the account without verifying the email — the attribute stays unverified, which is dangerous when email drives password reset or account linking. Reserve it for trusted/migrated accounts. See troubleshooting.md.

Quick Navigation

You want to...Go to
Create a user pool, sign-up/sign-in, MFA, password policy, app clientsuser-pools.md
Add hosted UI / managed login, OAuth flows, social or SAML login, callback URLs, custom domain (ACM in us-east-1)managed-login-oauth.md
Handle ID/access/refresh tokens, rotation, revocation, session termination (global sign-out vs revoke vs disable)tokens-and-sessions.md
Give the client temporary AWS credentials, guest access, role mappingidentity-pools.md
Protect an API Gateway API with Cognito tokens (and enforce custom claims in the backend)api-authorization.md
Add Cognito login in front of an Application Load Balancer (ALB authenticate-cognito)api-authorization.md
Machine-to-machine (client credentials) auth, resource servers, custom scopesmanaged-login-oauth.md
Create user pool groups and add users to them (cognito:groups, Precedence)user-pools.md
Customize claims, custom auth challenge flows, migrate users, validate sign-uplambda-triggers.md
Add passkey / WebAuthn sign-in (USER_AUTH flow, AllowedFirstAuthFactors, WebAuthn enrollment)passkeys.md
Configure threat protection — compromised-credentials block, adaptive auth (risk-based MFA), log delivery to CloudWatchthreat-protection.md
Something is broken (redirect, token, MFA, CORS, social login)troubleshooting.md

Common Workflows

"Add sign-up and login to my React app" → Create a user pool + a public app client (no secret), enable the hosted UI / managed login with the authorization code grant with PKCE, wire the Amplify client library. See user-pools.md and managed-login-oauth.md.

"Add Google / social login" → Register the social IdP on the user pool, map attributes, add the provider to the app client and hosted UI. See managed-login-oauth.md.

"Only authenticated users should call my API" → HTTP API → JWT authorizer; REST API → Cognito user pools authorizer. See api-authorization.md.

"Let the browser upload to S3 after login" → User pool for sign-in, then an identity pool to vend scoped temporary credentials. See identity-pools.md.

Troubleshooting

Error/SymptomLikely CauseQuick Fix
redirect_mismatch / redirect to wrong URL after loginCallback URL not registered, or scheme/trailing-slash/case differsAdd the exact callback URL (incl. scheme and path) to the app client's Allowed callback URLs
Token calls fail with "unable to verify secret hash"Client secret set on a public (SPA/mobile) clientRecreate the app client with no secret, or send SECRET_HASH from a confidential client
Users get 401 from API Gateway with a valid tokenWrong token type or audience/issuer mismatchHTTP JWT authorizer: issuer https://cognito-idp.{region}.amazonaws.com/{userPoolId}, audience = app client id; send the token the authorizer expects
CORS errors calling the hosted UI / token endpointBrowser calling /oauth2/token cross-origin, or missing CORS on your APIDo the code exchange with PKCE; don't proxy the token endpoint from the browser
Social login user "already exists" / attribute conflictSame email across providers creates separate usersEnable attribute mapping + account linking; treat email as non-unique across IdPs

Full tables in troubleshooting.md.

Security Considerations

  • Public clients (SPA/mobile): no client secret, authorization code grant with PKCE, request least-privilege scopes.

  • Enable MFA (TOTP or SMS), a strong password policy, and advanced security / threat protection where available.

  • Short access-token lifetime; enable refresh token rotation and token revocation; prefer cookieStorage over localStorage.

  • Identity pools: scope the authenticated IAM role tightly; disable unauthenticated (guest) access unless required.

  • Validate JWTs against the user pool JWKS (iss, aud/client_id, token_use, exp) on every protected request. Use a maintained library such as aws-jwt-verify rather than hand-rolling verification.

  • Set security headers on the app's web pages: Content-Security-Policy (restrict script sources to mitigate token-stealing XSS), Strict-Transport-Security (HSTS), X-Frame-Options/frame-ancestors (clickjacking on login pages), and X-Content-Type-Options: nosniff.

  • Enable logging and monitoring: CloudTrail for Cognito API events (sign-up/sign-in/admin), user pool threat protection (adaptive auth + event logging), CloudWatch alarms on failed/throttled auth, and API Gateway access logging for authorizer decisions.

  • All Cognito and API endpoints are HTTPS/TLS only; enable encryption at rest with a customer-managed KMS key (and restricted key access) on CloudWatch Log groups, SNS topics used for MFA/notifications, and any identity-pool-fronted upload buckets.

  • If using SNS for MFA/notification delivery, enable server-side encryption (KMS) on the topic, and keep SMS/email message content limited to what the recipient needs — don't include more PII than the message requires.

  • References: Amazon Cognito security features (user pools), Amazon Cognito security (top-level, incl. identity pools), and IAM/STS best practices.

Where to Look When This Skill Is Silent

When you need depth beyond this skill — exact parameter shapes, current limits, edge behaviors — fall back to the authoritative AWS sources rather than guessing. Pointers age much slower than content, so this map stays useful without the skill having to grow.

Not Covered By This Skill

  • Amplify Gen2 backend (defineAuth, amplify/auth.ts, npx ampx sandbox).

  • IAM policy/role/trust-policy authoring, STS, IAM Identity Center console SSO.

  • API Gateway route/integration setup and Lambda function implementation (this skill covers only the Cognito/JWT authorizer configuration and the purpose of Cognito Lambda triggers).

Files

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Requirements and compatibility

Works with: Claude Code, Claude apps, OpenAI Codex, GitHub Copilot, Cursor, Gemini CLI, Kiro, OpenCode, Goose, Amp, Roo Code, JetBrains Junie, Factory Droid, Devin (ex-Windsurf), Mistral Vibe, OpenHands, Letta

“Works with” means the tool reads the open Agent Skills format; a skill written for one tool may use features others lack.

Needs: Needs an MCP server, Needs Node.js

Security

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Attribution and licence

Published by
AWS
Publisher
AWS (Official)
Source
aws/agent-toolkit-for-aws · skills/core-skills/aws-auth · commit 0a218f8
Licence
Apache License 2.0 (redistribution allowed)
  • LICENSE (added by AutoGineer from LICENSE)
  • NOTICE (added by AutoGineer from NOTICE)
  • ATTRIBUTION.md (written by AutoGineer)
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